What Is Mediastinal Tumor?

Introduction

Topics that fall into the world of 'Tumours' may often be seen as daunting, confusing, and complex.  There is so much information,  with many new terms, and research that always seems to be changing. Today, we will try to make the topic of Mediastinal Tumours accessible and easy to understand.

Whether you're seeking information for yourself, a loved one, or just eager to expand your knowledge on this topic, this article aims to take you on a journey through what mediastinal tumours are, their causes and types, and their overall impact on health.

Overview

So, what are mediastinal tumours, you ask? In its essence, the mediastinum is a space within the chest that holds many important organs like the heart and the great blood vessels.¹ Sometimes, tumours can grow within this particular space. Tumours are abnormal masses of cells.2 These tumours can be either benign (not cancerous)3 or malignant (cancerous).4 Mediastinal masses are relatively rare, and their prevalence often varies between age groups.⁵

Risk factors of mediastinal tumours 

Determining the causes of mediastinal tumours can be difficult as tumour development is often a multifactorial process. However, there are risk factors which may play a role in tumour development. Despite more research being required to determine the exact genetic pathways, studies have found the contribution of certain genetic markers in some select mediastinal tumours.⁶ Other risk factors include family history and previous medical history of mediastinal tumours.⁷

Classifications of mediastinal tumours 

Mediastinal tumours are usually classified into one of three categories: 

• Classification based on the tissue of origin 
• Location (anterior (front), middle, posterior, (behind)) 
• Classification is based on whether it is cancerous or not.

Anterior mediastinal mass

Thymic carcinoma and thymoma 

Thymic Carcinomas and Thymomas are cancerous anterior mediastinal tumours.⁸ They develop in the thymus gland, a butterfly-shaped gland situated at the base of the neck.⁹ These are the most common cancers in the anterior mediastinum, accounting for 20% of all mediastinal tumours.¹⁰ Despite both cancers developing from the thymic epithelial cells, they have their differences.¹¹ Thymomas are slow-growing cells that rarely metastasise (grow past the thymus). They rarely affect children and are often associated with paraneoplastic diseases such as myasthenia gravis and Thymoma-associated autoimmune pure red cell aplasia.¹² However, thymic carcinomas are aggressive cancers that are prone to early metastasis. They occur most in adults aged 40-60 and are often more difficult to treat.¹¹

Thymic cysts 

Thymic cysts are benign anterior mediastinal tumours. They are rare tumours and are believed to arise from either a congenital or an inflammatory abnormality.¹³ Surgical Excision is the recommended treatment for thymic cysts.¹⁴

Lymphomas

Lymphomas are cancers of the lymphatic system.¹⁵ This includes both Hodgkin's Lymphoma and Non-Hodgkins Lymphoma.

Mediastinal germ cell tumour

These tumours are anterior mediastinal tumours that arise from reproductive cells called germ cells.¹⁶ There are many types of germ cell tumours; some are cancerous, and others are benign. Benign germ cell tumours include mature teratomas and dermoid cysts. Cancerous germ cell tumours are often split into two groups: seminoma germ cell tumours and non-seminoma germ cell tumours.¹⁶ 

Goitres

Goitres are swellings located in the anterior mediastinum due to a swollen thyroid. These are mostly benign growths but should be checked by your healthcare provider as there are many possible underlying causes of goitres such as hyperthyroidism, hypothyroidism and very rarely thyroid cancer.¹⁷

Middle mediastinal mass

• Bronchogenic Cysts: Bronchogenic Cysts are mediastinal masses that are derived from the embryological remnants of the respiratory tract. They are often filled with mucus.¹⁸ 
• Pericardial Cysts: This is a congenital abnormality where a fluid-filled sac, a thin sac that surrounds the heart, grows in the pericardium.¹⁹
• Oesophageal Tumours: Tumours can develop within your oesophagus, and they can be either benign or malignant. The most common type of benign oesophageal tumour is a leiomyoma.²⁰ Adenocarcinomas are the most prevalent malignant oesophageal tumour.²¹
• Tracheal Tumours: Tumours can develop within your trachea, and they can be either benign or malignant.    

Posterior mediastinal mass

• Neurogenic Tumours: Neurenteric cysts are rare, congenital lesions of the spinal axis. Patients suffering from these conditions often present with weakness, pins and needles (paresthesia), incontinence and in severe cases, headaches due to raised intracranial pressure.²²
• Mediastinal Lymphadenopathy:  They are caused by the swelling of the lymph nodes within the chest. These lymph nodes can swell secondary to either benign or malignant conditions.²³ 

Signs and symptoms of mediastinal tumours 

Mediastinum tumours are often asymptomatic and present incidentally on chest X-rays^?? However, symptoms do commonly arise due to compression of the tumour on surrounding structures within the body. 

Symptoms include:

• Chest Pain 
• Hoarseness 
• Night Sweats 
• Shortness of Breath 
• Fever 
• Haemoptysis 
• Cough 

Diagnosis 

Diagnosis of mediastinal tumours is achieved comprehensively, beginning with a detailed medical history, physical exam and bloodwork. Your healthcare provider may also provide further investigations if clinical findings are consistent with a clinical mass. These include: 

• Chest X-rays: A short painless procedure where the mediastinum is imaged by your healthcare provider.²⁴
• Biopsies: Your healthcare provider may perform a procedure where tissues are removed to be further examined. This can be done through processes called needle biopsy, endobronchial ultrasound or mediastinoscopy with biopsy.
• Computerised Tomography (CT) Scan: Your healthcare provider may use a CT scan to image the mass in more detail in relation to surrounding structures.²⁵
• Magnetic Resonance Imaging: Your healthcare provider may conduct an MRI scan to determine how a suspected mediastinal mass may be affecting surrounding structures. It may also reveal the type of tissue that makes up the mass.²⁵

Treatment

Treatment options for mediastinal tumours are decisions made on a case-by-case basis by a  multidisciplinary team. This means that surgeons, oncologists, radiologists, and other members of a  healthcare team discuss your individual case and devise a tailored approach. Their agreed method often depends on several factors, such as tumour type, location, stage (if cancerous), and the presence of symptoms. 

Treatment options include:

Surgical Resection: Surgery is the primary treatment method used in many cases. It is mostly recommended for cancerous tumours, tumours compressing nearby structures, and symptomatic tumours. Examples of tumours often requiring surgical resection are thymomas, thymic carcinomas, and neurogenic tumours. Your healthcare provider might suggest conducting a procedure called a sternotomy, where an incision through the breastbone, or a minimally invasive approach called video-assisted thoracoscopic surgery (VATS) for treating mediastinal tumours.

Radiotherapy: Radiotherapy is another possible treatment option for cancerous masses like thymomas, thymic cancer, or lymphomas. This is where high-energy X-ray beams are directed at the tumour(s) to destroy them. Radiation may be administered before surgery as neoadjuvant therapy, after therapy as adjuvant therapy or as a standalone treatment. This clinical decision often depends on the stage progression of the cancer.²⁶

Chemotherapy: Chemotherapeutic agents are specifically used to target and eradicate cancerous cells. This technique is commonly employed to treat thymic cancers.¹¹

In cases where the mediastinal mass results from an infection, such as lymphadenopathy, antibiotics may be prescribed.²⁷

If the tumour is benign and mostly asymptomatic, your healthcare provider might opt for watchful waiting. This method closely monitors the tumour's progression without immediate intervention.²⁸

It is important to consult with your healthcare providers to determine the most suitable treatment plan based on your individual medical needs.

When Should I contact a doctor? 

If you suspect you or any of your loved ones are experiencing any symptoms that may be related to a mediastinal mass, it's important to see a doctor promptly for further investigation. While many mediastinal tumours are asymptomatic and benign, some masses do require medical attention. 

Summary 

Mediastinal tumours are abnormal masses of cells that can grow in the space within the chest called the mediastinum. The term mediastinal mass encompasses many conditions which can either be benign or malignant. Symptoms can often arise due to compression on surrounding structures. However, many tumours can be asymptomatic. Diagnosis involves a detailed medical history, physical exam, and various imaging and biopsy techniques. Treatment options are determined through multidisciplinary participation to decide the best course of action based on the individual.